Hydraulic jack is a type of hoisting equipment widely applied to lift of vehicles or heavy goods. Existing hydraulic jack normally adopts the dynamic oil cylinder using single-post pump core and pump body hole to realize the clearance fit, which is characterized by simple structure and low technical cost. However, it is far from being able to satisfy the functional requirement for quick ascending as required by the hydraulic jack under zero or light load. As disclosed by Chinese patent ZL200620075069.1, the dual-speed vertical hydraulic jack, oil sucked by the pump core of hydraulic system of zero load or light load under low pressure can be fully pressed into the working oil chamber; whereas, partial oil is pressed into the upper chamber of the pump cylinder when the system is under high pressure. Partial oil pressed into the chamber of working oil cylinder can drive the piston assembly to hoist the loaded goods stably and quickly under the action of oil of minimal flux. As the structural technique of the pump core and pump body is so complicated, the high fabrication cost would affect the competition power of the product in international market.